A magnetically actuated valve for centrifugal microfluidic applications

A novel magnetically actuated valving system was designed, fabricated, and tested. It is very suitable for use in centrifugal microfluidic platforms. The fluidic structure of the valve was fabricated by polydimethylsiloxane (PDMS) replica molding process and sandwiched between two permanent magnets. The working principle is based on the deformation of the PDMS micro-channel under the magnetic force. A flyball governor was integrated in the platform to control the distance between the magnets during operation. When the flyball governor is stationary or spins at low speed, the two facing magnets produce enough magnetic force to overcome the elastic force of the covering membrane. The deformation of the covering membrane can therefore completely block the flow channel. When the spinning speed increases to a critical value, the centrifugal force helps to pull the bottom-side magnet away, which reduces the magnetic force and consequently opens the flow channel of the valve. Therefore, the valve is controlled by manipulating the spinning speed of the flyball governor. Its burst frequency can be easily tuned for various load settings. The actuation of four valves integrated Lab-on-CD system was characterized with respect to the mass of the flyball, the intensity of the magnetic field and the preload of the supporting spring. The experimental results show that the burst frequency ranges from 800 rpm to 1600 rpm for the channel with a cross-section of 100 μm wide × 200 μm high. This new valve design offers several advantages including simple fabrication, multiple use, robust control, universal application and easy integration. It also attains the flexibility to switch between open state and closed state during operation, making it capable of complex fluid handling. Therefore, the valve can be used in various Lab-on-CD systems for biological, chemical or medical applications.